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- // SPDX-License-Identifier: GPL-2.0-or-later
- /*
- * SN Platform GRU Driver
- *
- * MMUOPS callbacks + TLB flushing
- *
- * This file handles emu notifier callbacks from the core kernel. The callbacks
- * are used to update the TLB in the GRU as a result of changes in the
- * state of a process address space. This file also handles TLB invalidates
- * from the GRU driver.
- *
- * Copyright (c) 2008 Silicon Graphics, Inc. All Rights Reserved.
- */
- #include <linux/kernel.h>
- #include <linux/list.h>
- #include <linux/spinlock.h>
- #include <linux/mm.h>
- #include <linux/slab.h>
- #include <linux/device.h>
- #include <linux/hugetlb.h>
- #include <linux/delay.h>
- #include <linux/timex.h>
- #include <linux/srcu.h>
- #include <asm/processor.h>
- #include "gru.h"
- #include "grutables.h"
- #include <asm/uv/uv_hub.h>
- #define gru_random() get_cycles()
- /* ---------------------------------- TLB Invalidation functions --------
- * get_tgh_handle
- *
- * Find a TGH to use for issuing a TLB invalidate. For GRUs that are on the
- * local blade, use a fixed TGH that is a function of the blade-local cpu
- * number. Normally, this TGH is private to the cpu & no contention occurs for
- * the TGH. For offblade GRUs, select a random TGH in the range above the
- * private TGHs. A spinlock is required to access this TGH & the lock must be
- * released when the invalidate is completes. This sucks, but it is the best we
- * can do.
- *
- * Note that the spinlock is IN the TGH handle so locking does not involve
- * additional cache lines.
- *
- */
- static inline int get_off_blade_tgh(struct gru_state *gru)
- {
- int n;
- n = GRU_NUM_TGH - gru->gs_tgh_first_remote;
- n = gru_random() % n;
- n += gru->gs_tgh_first_remote;
- return n;
- }
- static inline int get_on_blade_tgh(struct gru_state *gru)
- {
- return uv_blade_processor_id() >> gru->gs_tgh_local_shift;
- }
- static struct gru_tlb_global_handle *get_lock_tgh_handle(struct gru_state
- *gru)
- {
- struct gru_tlb_global_handle *tgh;
- int n;
- preempt_disable();
- if (uv_numa_blade_id() == gru->gs_blade_id)
- n = get_on_blade_tgh(gru);
- else
- n = get_off_blade_tgh(gru);
- tgh = get_tgh_by_index(gru, n);
- lock_tgh_handle(tgh);
- return tgh;
- }
- static void get_unlock_tgh_handle(struct gru_tlb_global_handle *tgh)
- {
- unlock_tgh_handle(tgh);
- preempt_enable();
- }
- /*
- * gru_flush_tlb_range
- *
- * General purpose TLB invalidation function. This function scans every GRU in
- * the ENTIRE system (partition) looking for GRUs where the specified MM has
- * been accessed by the GRU. For each GRU found, the TLB must be invalidated OR
- * the ASID invalidated. Invalidating an ASID causes a new ASID to be assigned
- * on the next fault. This effectively flushes the ENTIRE TLB for the MM at the
- * cost of (possibly) a large number of future TLBmisses.
- *
- * The current algorithm is optimized based on the following (somewhat true)
- * assumptions:
- * - GRU contexts are not loaded into a GRU unless a reference is made to
- * the data segment or control block (this is true, not an assumption).
- * If a DS/CB is referenced, the user will also issue instructions that
- * cause TLBmisses. It is not necessary to optimize for the case where
- * contexts are loaded but no instructions cause TLB misses. (I know
- * this will happen but I'm not optimizing for it).
- * - GRU instructions to invalidate TLB entries are SLOOOOWWW - normally
- * a few usec but in unusual cases, it could be longer. Avoid if
- * possible.
- * - intrablade process migration between cpus is not frequent but is
- * common.
- * - a GRU context is not typically migrated to a different GRU on the
- * blade because of intrablade migration
- * - interblade migration is rare. Processes migrate their GRU context to
- * the new blade.
- * - if interblade migration occurs, migration back to the original blade
- * is very very rare (ie., no optimization for this case)
- * - most GRU instruction operate on a subset of the user REGIONS. Code
- * & shared library regions are not likely targets of GRU instructions.
- *
- * To help improve the efficiency of TLB invalidation, the GMS data
- * structure is maintained for EACH address space (MM struct). The GMS is
- * also the structure that contains the pointer to the mmu callout
- * functions. This structure is linked to the mm_struct for the address space
- * using the mmu "register" function. The mmu interfaces are used to
- * provide the callbacks for TLB invalidation. The GMS contains:
- *
- * - asid[maxgrus] array. ASIDs are assigned to a GRU when a context is
- * loaded into the GRU.
- * - asidmap[maxgrus]. bitmap to make it easier to find non-zero asids in
- * the above array
- * - ctxbitmap[maxgrus]. Indicates the contexts that are currently active
- * in the GRU for the address space. This bitmap must be passed to the
- * GRU to do an invalidate.
- *
- * The current algorithm for invalidating TLBs is:
- * - scan the asidmap for GRUs where the context has been loaded, ie,
- * asid is non-zero.
- * - for each gru found:
- * - if the ctxtmap is non-zero, there are active contexts in the
- * GRU. TLB invalidate instructions must be issued to the GRU.
- * - if the ctxtmap is zero, no context is active. Set the ASID to
- * zero to force a full TLB invalidation. This is fast but will
- * cause a lot of TLB misses if the context is reloaded onto the
- * GRU
- *
- */
- void gru_flush_tlb_range(struct gru_mm_struct *gms, unsigned long start,
- unsigned long len)
- {
- struct gru_state *gru;
- struct gru_mm_tracker *asids;
- struct gru_tlb_global_handle *tgh;
- unsigned long num;
- int grupagesize, pagesize, pageshift, gid, asid;
- /* ZZZ TODO - handle huge pages */
- pageshift = PAGE_SHIFT;
- pagesize = (1UL << pageshift);
- grupagesize = GRU_PAGESIZE(pageshift);
- num = min(((len + pagesize - 1) >> pageshift), GRUMAXINVAL);
- STAT(flush_tlb);
- gru_dbg(grudev, "gms %p, start 0x%lx, len 0x%lx, asidmap 0x%lx\n", gms,
- start, len, gms->ms_asidmap[0]);
- spin_lock(&gms->ms_asid_lock);
- for_each_gru_in_bitmap(gid, gms->ms_asidmap) {
- STAT(flush_tlb_gru);
- gru = GID_TO_GRU(gid);
- asids = gms->ms_asids + gid;
- asid = asids->mt_asid;
- if (asids->mt_ctxbitmap && asid) {
- STAT(flush_tlb_gru_tgh);
- asid = GRUASID(asid, start);
- gru_dbg(grudev,
- " FLUSH gruid %d, asid 0x%x, vaddr 0x%lx, vamask 0x%x, num %ld, cbmap 0x%x\n",
- gid, asid, start, grupagesize, num, asids->mt_ctxbitmap);
- tgh = get_lock_tgh_handle(gru);
- tgh_invalidate(tgh, start, ~0, asid, grupagesize, 0,
- num - 1, asids->mt_ctxbitmap);
- get_unlock_tgh_handle(tgh);
- } else {
- STAT(flush_tlb_gru_zero_asid);
- asids->mt_asid = 0;
- __clear_bit(gru->gs_gid, gms->ms_asidmap);
- gru_dbg(grudev,
- " CLEARASID gruid %d, asid 0x%x, cbtmap 0x%x, asidmap 0x%lx\n",
- gid, asid, asids->mt_ctxbitmap,
- gms->ms_asidmap[0]);
- }
- }
- spin_unlock(&gms->ms_asid_lock);
- }
- /*
- * Flush the entire TLB on a chiplet.
- */
- void gru_flush_all_tlb(struct gru_state *gru)
- {
- struct gru_tlb_global_handle *tgh;
- gru_dbg(grudev, "gid %d\n", gru->gs_gid);
- tgh = get_lock_tgh_handle(gru);
- tgh_invalidate(tgh, 0, ~0, 0, 1, 1, GRUMAXINVAL - 1, 0xffff);
- get_unlock_tgh_handle(tgh);
- }
- /*
- * MMUOPS notifier callout functions
- */
- static int gru_invalidate_range_start(struct mmu_notifier *mn,
- const struct mmu_notifier_range *range)
- {
- struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
- ms_notifier);
- STAT(mmu_invalidate_range);
- atomic_inc(&gms->ms_range_active);
- gru_dbg(grudev, "gms %p, start 0x%lx, end 0x%lx, act %d\n", gms,
- range->start, range->end, atomic_read(&gms->ms_range_active));
- gru_flush_tlb_range(gms, range->start, range->end - range->start);
- return 0;
- }
- static void gru_invalidate_range_end(struct mmu_notifier *mn,
- const struct mmu_notifier_range *range)
- {
- struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
- ms_notifier);
- /* ..._and_test() provides needed barrier */
- (void)atomic_dec_and_test(&gms->ms_range_active);
- wake_up_all(&gms->ms_wait_queue);
- gru_dbg(grudev, "gms %p, start 0x%lx, end 0x%lx\n",
- gms, range->start, range->end);
- }
- static struct mmu_notifier *gru_alloc_notifier(struct mm_struct *mm)
- {
- struct gru_mm_struct *gms;
- gms = kzalloc(sizeof(*gms), GFP_KERNEL);
- if (!gms)
- return ERR_PTR(-ENOMEM);
- STAT(gms_alloc);
- spin_lock_init(&gms->ms_asid_lock);
- init_waitqueue_head(&gms->ms_wait_queue);
- return &gms->ms_notifier;
- }
- static void gru_free_notifier(struct mmu_notifier *mn)
- {
- kfree(container_of(mn, struct gru_mm_struct, ms_notifier));
- STAT(gms_free);
- }
- static const struct mmu_notifier_ops gru_mmuops = {
- .invalidate_range_start = gru_invalidate_range_start,
- .invalidate_range_end = gru_invalidate_range_end,
- .alloc_notifier = gru_alloc_notifier,
- .free_notifier = gru_free_notifier,
- };
- struct gru_mm_struct *gru_register_mmu_notifier(void)
- {
- struct mmu_notifier *mn;
- mn = mmu_notifier_get_locked(&gru_mmuops, current->mm);
- if (IS_ERR(mn))
- return ERR_CAST(mn);
- return container_of(mn, struct gru_mm_struct, ms_notifier);
- }
- void gru_drop_mmu_notifier(struct gru_mm_struct *gms)
- {
- mmu_notifier_put(&gms->ms_notifier);
- }
- /*
- * Setup TGH parameters. There are:
- * - 24 TGH handles per GRU chiplet
- * - a portion (MAX_LOCAL_TGH) of the handles are reserved for
- * use by blade-local cpus
- * - the rest are used by off-blade cpus. This usage is
- * less frequent than blade-local usage.
- *
- * For now, use 16 handles for local flushes, 8 for remote flushes. If the blade
- * has less tan or equal to 16 cpus, each cpu has a unique handle that it can
- * use.
- */
- #define MAX_LOCAL_TGH 16
- void gru_tgh_flush_init(struct gru_state *gru)
- {
- int cpus, shift = 0, n;
- cpus = uv_blade_nr_possible_cpus(gru->gs_blade_id);
- /* n = cpus rounded up to next power of 2 */
- if (cpus) {
- n = 1 << fls(cpus - 1);
- /*
- * shift count for converting local cpu# to TGH index
- * 0 if cpus <= MAX_LOCAL_TGH,
- * 1 if cpus <= 2*MAX_LOCAL_TGH,
- * etc
- */
- shift = max(0, fls(n - 1) - fls(MAX_LOCAL_TGH - 1));
- }
- gru->gs_tgh_local_shift = shift;
- /* first starting TGH index to use for remote purges */
- gru->gs_tgh_first_remote = (cpus + (1 << shift) - 1) >> shift;
- }
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